Which building products should be bought online or from the craftsman?

Online retailers are also retailers, I see that completely unemotionally. The real question here is:

Do I A) buy the shower (as an example) as a complete package including delivery and installation. Or do I B) separately purchase a shower, take care of the delivery, and then as the third part handle the installation. Needless to say, A) is stress-free (get one quote, place one order, do one inspection, done), whereas B) is considerably more complicated (the whole mess three times plus the difficulty of finding someone to install provided materials*). And of course, A) is also easier in the event of warranty claims, because the installer and delivery cannot pass the buck to each other, as they definitely would in B). Of course, B) must be significantly(!) cheaper for it to be worthwhile...

* We are in a boom period, please keep that in mind. Customer threatens with an order, craftsman assigns a number... ;-).

Everything that you can install yourself, I would definitely buy online. Just with the electrical stuff, we saved about 40%, which is several thousand. The same goes for all the bathroom ceramics, etc., these also cost almost 50% less online. We also saved several thousand on the tiles by buying online. I would just clarify beforehand whether you can install it yourself or otherwise arrange for the material to be installed at a reasonable price, so that you don’t end up sitting on piles of material that no one wants to install for you...

We also saved several thousand on the tiles by buying online.

Were you able to look at and touch the tiles beforehand, or were they only ordered based on the online photo?

Did you have the tiles to look at and touch beforehand or were they only ordered based on the online photo?

For example, for the wood-look tiles we visited numerous stores but didn’t find anything we liked anywhere. On the internet, I then saw some nice tiles, and the online retailer, I even think for free, sent up to 3 samples. We then ordered one of the three, but not the one we had preferred according to the photos, though from the same series.
In the specialist trade, the price was about 90.- €, while by shipping it was under 50.- €.
We bought some of the bathroom tiles in specialist stores since after negotiation they were only slightly more expensive, but for the main bathroom we also ordered (after seeing them in the store) because here it was about 30% cheaper.

Hi,
we also removed quite a bit from the [GU] scope:
Interior doors,
parquet flooring,
sanitary fixtures, but only the toilets and sinks. Shower rods, walk-in shower, and bathtub are covered by the [GU].
Interior doors and parquet flooring will be installed by a professional with me as an assistant.
I got the materials from local dealers, who even undercut every online price significantly!
Toilets and sinks through the classic "Hornbach routine". I'll install those myself.
Tiles came from a tile studio that works with the [GU]. I would always buy locally, good advice is priceless there. In the end, the tile prices were also lower than the same tiles online.

Best regards,

Andreas